scholarly journals A Natural Occurring Mouse Model with Adgrv1 Mutation of Usher Syndrome 2C and Characterization of its Recombinant Inbred Strains

2018 ◽  
Vol 47 (5) ◽  
pp. 1883-1897 ◽  
Author(s):  
Weiming Yan ◽  
Pan Long ◽  
Tao Chen ◽  
Wei Liu ◽  
Lu Yao ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Inner Ear ◽  
Retinal Degeneration ◽  
Western Blotting ◽  
Hair Cells ◽  
Recombinant Inbred ◽  
Usher Syndrome ◽  
Inbred Strains ◽  
Outer Hair Cells ◽  
Recombinant Inbred Strains

Background/Aims: Our laboratory discovered a Kunming mouse with enormous electroretinogram (ERG) defects. Its auditory brainstem response (ABR) threshold was significantly elevated and closely resembled the features of Usher syndrome (USH). This study sought to cross these USH-like mice (named KMush/ush mice) with CBA/CaJ mice to establish recombinant inbred strains and identify their phenotypes and genotypes. Methods: KMush/ush mice were crossed with CBA/CaJ mice to establish inbred strains by sibling mating. ERG, ABR, ocular fundus morphology, histological examinations of the retina and inner ear, quantitative real-time polymerase chain reaction, western blotting, and exon sequencing were performed to assess the phenotypes and genotypes of the offspring strains. Results: The F1 hybrids from crossing KMush/ush and CBA/CaJ mice had normal ERG and ABR responses. The F2 offspring from intercrossing the F1 mice showed a segregation of the retinitis pigmentosa (RP) and hearing loss phenotypes. The CBA-1ush/ush mice had an RP phenotype that was characterized by a vanished ERG waveform and loss of the outer nuclear layer. Their Pde6b gene had a nonsense mutation that resulted in the failure of protein production in western blotting. However, the ABR threshold of this strain of mice was normal. The CBA-2ush/ush mice had normal retinal function and architecture. Their ABR threshold was increased, with a dramatic degeneration of the stereocilia bundles in the outer hair cells of the inner ear. Whole exome sequencing and exon sequencing revealed a deletion of one base pair in exon 31 of the Adgrv1 gene, which would result in the premature termination of protein encoding. The level of Adgrv1 mRNA was reduced in the CBA-2ush/ush mice. The CBA-3ush/ush mice had phenotypes of RP, elevated ABR threshold, and degeneration of the stereocilia bundles in the outer hair cells. They were closely associated with the nonsense mutations of Pde6b and Adgrv1, respectively. Conclusion: We isolated a mouse strain with hearing loss from inbred mice with retinal degeneration and established it as a recombinant inbred strain with a spontaneous mutation in Adgrv1, the human Usher syndrome 2C gene. The retinal degeneration was cause by a mutation in Pde6b, while the hearing loss was caused by a mutation in Adgrv1.

scholarly journals Immunohistochemistry localises myosin-7a to cochlear efferent boutons

2022 ◽  
Vol 7 ◽  
pp. 1
Author(s):  
Piotr Sirko ◽  
Andrei S. Kozlov
Keyword(s):  
Hearing Loss ◽  
Vestibular System ◽  
Hair Cells ◽  
Usher Syndrome ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Actin Binding ◽  
Adult Rat ◽  
Cochlear Gain ◽  
Medial Olivocochlear

Background: Myosin 7a is an actin-binding motor protein involved in the formation of hair-cell stereocilia both in the cochlea and in the vestibular system. Mutations in myosin 7a are linked to congenital hearing loss and are present in 50% of Type-1 Usher syndrome patients who suffer from progressive hearing loss and vestibular system dysfunction. Methods: Myosin 7a is often used to visualise sensory hair cells due to its well characterised and localised expression profile. We thus conducted myosin-7a immunostaining across all three turns of the adult rat organ of Corti to visualise hair cells. Results: As expected, we observed myosin 7a staining in both inner and outer hair cells. Unexpectedly, we also observed strong myosin 7a staining in the medial olivocochlear efferent synaptic boutons contacting the outer hair cells. Efferent bouton myosin-7a staining was present across all three turns of the cochlea. We verified this localisation by co-staining with a known efferent bouton marker, the vesicular acetylcholine transporter. Conclusions: In addition to its role in stereocilia formation and maintenance, myosin 7a or certain myosin-7a expression variants might play a role in efferent synaptic transmission in the cochlea and thus ultimately influence cochlear gain regulation. Our immunohistochemistry results should be validated with other methods to confirm these serendipitous findings.

Association of Conductive Hearing Loss with the Structural Changes in the Organ of Corti

ORL ◽  
2021 ◽  
pp. 1-8
Author(s):  
Sinan Eroglu ◽  
Rasit Cevizci ◽  
Handan Turan Dizdar ◽  
Hasan Deniz Tansuker ◽  
Erdogan Bulut ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Inner Ear ◽  
Cell Morphology ◽  
Hair Cells ◽  
Structural Changes ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

<b><i>Objective:</i></b> The aim of the study was to evaluate the association of conductive hearing loss (CHL) with the structural changes in the organ of Corti. <b><i>Methods:</i></b> Twenty ears of 10 healthy adult Wistar albino rats were included in the study. The right ears (<i>n</i> = 10) of the animals served as controls (group 1), and no surgical intervention was performed in these ears. A tympanic membrane perforation without annulus removal was performed under operative microscope on the left ears (<i>n</i> = 5) in 5 of 10 animals (group 2). A tympanic membrane perforation with annulus removal was performed under operative microscope on the left ears (<i>n</i> = 5) of the remaining 5 animals (group 3). Auditory brainstem response testing was performed in the animals before the interventions. After 3 months, the animals were sacrificed, their temporal bones were removed, and inner ears were investigated using scanning electron microscopy (SEM). The organ of Corti was evaluated from the cochlear base to apex in the modiolar axis, and the parameters were scored semiquantitatively. <b><i>Results:</i></b> In group 1, the pre- and post-intervention hearing thresholds were similar (<i>p</i> &#x3e; 0.05). In group 2, a hearing decrease of at least 5 dB was encountered in all test frequencies (<i>p</i> &#x3e; 0.05). In group 3, at the frequency range of 2–32 kHz, there was a significant hearing loss after 3 months (<i>p</i> &#x3c; 0.01). After 3 months, the hearing thresholds in group 2 and 3 were higher than group 1 (<i>p</i> &#x3c; 0.01). The hearing threshold in group 3 was higher than group 2 (<i>p</i> &#x3c; 0.01). On SEM evaluation, the general cell morphology and stereocilia of the outer hair cells were preserved in all segments of the cochlea in group 1 with a mean SEM score of 0.2. There was segmental degeneration in the general cell morphology and outer hair cells in group 2 with a mean SEM score of 2.2. There was widespread degeneration in the general cell morphology and outer hair cells in group 3 with a mean SEM score of 3.2. The SEM scores of group 2 and 3 were significantly higher than group 1 (<i>p</i> &#x3c; 0.05). The SEM scores of group 3 were significantly higher than group 2 (<i>p</i> &#x3c; 0.05). <b><i>Conclusion:</i></b> CHL may be associated with an inner ear damage. The severity of damage appears to be associated with severity and duration of CHL. Early correction of CHL is advocated in order to reverse or prevent progression of the inner ear damage, which will enhance the success rates of hearing restoration surgeries. Subjective differences and compliance of the hearing aid users may be due to the impact of CHL on inner ear structures.

scholarly journals Inner Ear and Muscle Developmental Defects in Smpx-Deficient Zebrafish Embryos

2021 ◽  
Vol 22 (12) ◽  
pp. 6497
Author(s):  
Anna Ghilardi ◽  
Alberto Diana ◽  
Renato Bacchetta ◽  
Nadia Santo ◽  
Miriam Ascagni ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Inner Ear ◽  
Hair Cells ◽  
Muscle Fibers ◽  
Underlying Mechanism ◽  
Loss Of Function ◽  
Zebrafish Model ◽  
Developmental Defects ◽  
Inner Ear Development ◽  
Syndromic Hearing Loss

The last decade has witnessed the identification of several families affected by hereditary non-syndromic hearing loss (NSHL) caused by mutations in the SMPX gene and the loss of function has been suggested as the underlying mechanism. In the attempt to confirm this hypothesis we generated an Smpx-deficient zebrafish model, pointing out its crucial role in proper inner ear development. Indeed, a marked decrease in the number of kinocilia together with structural alterations of the stereocilia and the kinocilium itself in the hair cells of the inner ear were observed. We also report the impairment of the mechanotransduction by the hair cells, making SMPX a potential key player in the construction of the machinery necessary for sound detection. This wealth of evidence provides the first possible explanation for hearing loss in SMPX-mutated patients. Additionally, we observed a clear muscular phenotype consisting of the defective organization and functioning of muscle fibers, strongly suggesting a potential role for the protein in the development of muscle fibers. This piece of evidence highlights the need for more in-depth analyses in search for possible correlations between SMPX mutations and muscular disorders in humans, thus potentially turning this non-syndromic hearing loss-associated gene into the genetic cause of dysfunctions characterized by more than one symptom, making SMPX a novel syndromic gene.

scholarly journals Ultrasound Microbubbles Enhance the Efficacy of Insulin-Like Growth Factor-1 Therapy for the Treatment of Noise-Induced Hearing Loss

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3626
Author(s):  
Yi-Chun Lin ◽  
Yuan-Yung Lin ◽  
Hsin-Chien Chen ◽  
Chao-Yin Kuo ◽  
Ai-Ho Liao ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Growth Factor ◽  
Inner Ear ◽  
Outer Hair Cells ◽  
Round Window Membrane ◽  
Insulin Like Growth Factor ◽  
Noise Induced Hearing Loss ◽  
Ear Diseases ◽  
Brainstem Response ◽  
Ultrasound Microbubbles

The application of insulin-like growth factor 1 (IGF-1) to the round window membrane (RWM) is an emerging treatment for inner ear diseases. RWM permeability is the key factor for efficient IGF-1 delivery. Ultrasound microbubbles (USMBs) can increase drug permeation through the RWM. In the present study, the enhancing effect of USMBs on the efficacy of IGF-1 application and the treatment effect of USMB-mediated IGF-1 delivery for noise-induced hearing loss (NIHL) were investigated. Forty-seven guinea pigs were assigned to three groups: the USM group, which received local application of recombinant human IGF-1 (rhIGF-1, 10 µg/µL) following application of USMBs to the RWM; the RWS group, which received IGF-1 application alone; and the saline-treated group. The perilymphatic concentration of rhIGF-1 in the USM group was 1.95- and 1.67- fold of that in the RWS group, 2 and 24 h after treatment, respectively. After 5 h of 118 dB SPL noise exposure, the USM group had the lowest threshold shift in auditory brainstem response, least loss of cochlear outer hair cells, and least reduction in the number of synaptic ribbons on postexposure day 28 among the three groups. The combination of USMB and IGF-1 led to a better therapeutic response to NIHL. Two hours after treatment, the USM group had significantly higher levels of Akt1 and Mapk3 gene expression than the other two groups. The most intense immunostaining for phosphor-AKT and phospho-ERK1/2 was detected in the cochlea in the USM group. These results suggested that USMB can be applied to enhance the efficacy of IGF-1 therapy in the treatment of inner ear diseases.

GENETIC ANALYSIS OF PLASMA CORTICOSTERONE LEVELS IN TWO INBRED STRAINS OF MICE

1972 ◽  
Vol 55 (2) ◽  
pp. 415-420 ◽  
Author(s):  
B. E. ELEFTHERIOU ◽  
D. W. BAILEY
Keyword(s):  
Genetic Analysis ◽  
Recombinant Inbred ◽  
Epistatic Interaction ◽  
Genetic Model ◽  
Inbred Strains ◽  
Plasma Corticosterone ◽  
Experimental Results ◽  
Recombinant Inbred Strains ◽  
Inbred Strains Of Mice

SUMMARY Plasma corticosterone levels were determined fluorometrically in mice of two unrelated highly inbred strains, C57BL/6By and BALB/cBy, and in seven of their derived recombinant-inbred strains as well as their F1 hybrid and backcross generations necessary to arrive at a genetic model for plasma corticosterone levels. It was concluded that the simplest genetic model, and one which fits the experimental results, was one which assumed that plasma corticosterone levels are controlled genetically by two loci with the epistatic interaction indicating dependency of pathways of action for the two genes.

Hes1 is a negative regulator of inner ear hair cell differentiation

Development ◽  
2000 ◽  
Vol 127 (21) ◽  
pp. 4551-4560 ◽  
Author(s):  
J.L. Zheng ◽  
J. Shou ◽  
F. Guillemot ◽  
R. Kageyama ◽  
W.Q. Gao
Keyword(s):  
Cell Differentiation ◽  
Hair Cell ◽  
Inner Ear ◽  
Cell Fate ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Negative Regulator ◽  
Pcr Analysis ◽  
Loss Of Function ◽  
Hair Cell Differentiation

Hair cell fate determination in the inner ear has been shown to be controlled by specific genes. Recent loss-of-function and gain-of-function experiments have demonstrated that Math1, a mouse homolog of the Drosophila gene atonal, is essential for the production of hair cells. To identify genes that may interact with Math1 and inhibit hair cell differentiation, we have focused on Hes1, a mammalian hairy and enhancer of split homolog, which is a negative regulator of neurogenesis. We report here that targeted deletion of Hes1 leads to formation of supernumerary hair cells in the cochlea and utricle of the inner ear. RT-PCR analysis shows that Hes1 is expressed in inner ear during hair cell differentiation and its expression is maintained in adulthood. In situ hybridization with late embryonic inner ear tissue reveals that Hes1 is expressed in supporting cells, but not hair cells, of the vestibular sensory epithelium. In the cochlea, Hes1 is selectively expressed in the greater epithelial ridge and lesser epithelial ridge regions which are adjacent to inner and outer hair cells. Co-transfection experiments in postnatal rat explant cultures show that overexpression of Hes1 prevents hair cell differentiation induced by Math1. Therefore Hes1 can negatively regulate hair cell differentiation by antagonizing Math1. These results suggest that a balance between Math1 and negative regulators such as Hes1 is crucial for the production of an appropriate number of inner ear hair cells.

High-Voltage Electron Microscopic Study of the Inner Ear: Technique and Preliminary Results

1983 ◽  
Vol 92 (1_suppl) ◽  
pp. 3-12 ◽  
Author(s):  
Tomonori Takasaka ◽  
Hideich Shinkawa ◽  
Kozo Watanuki ◽  
Sho Hashimoto ◽  
Kazutomo Kawamoto
Keyword(s):  
Electron Microscopy ◽  
Hair Cell ◽  
Inner Ear ◽  
High Voltage ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Preliminary Results ◽  
Voltage Electron ◽  
Cuticular Plate

The technique and some preliminary results of the application of high-voltage electron microscopy (HVEM) to the study of inner ear morphology in the guinea pig are reported in this paper. The main advantage of HVEM is that sharp images of thicker specimens can be obtained because of the greater penetrating power of high energy electrons. The optimum thickness of the sections examined with an accelerating voltage of 1,000 kV was found to be between 500 to 800 nm. The sections below 500 nm in thickness often had insufficient contrast, while those above 800 nm were rather difficult to interpret due to overlap of images of the organelles. The whole structure of the sensory hairs from the tip to the rootlet was more frequently observed in the 800-nm thick sections. Thus the fine details of the hair attachment to the tectorial membrane as well as the hair rootlet extension into the cuticular plate could be thoroughly studied in the HVEM. In specimens fixed in aldehyde containing 2% tannic acid, the attachment of the tips of the outer hair cell stereocilia to the tectorial membrane was observed. For the inner hair cells, however, the tips of the hairs were separated from the undersurface of the tectorial membrane. The majority of the rootlets of the outer hair cells terminated at the midportion of the cuticular plate, while most of the inner hair cell rootlets traversed the entire width of the cuticular plate and extended into the apical cytoplasm. These differences in ultrastructural appearance may indicate that the two kinds of hair cells play different roles in the acoustic transduction process. The three-dimensional arrangement of the nerve endings on the hair cells was also studied by the serial thick-sectioning technique in the HVEM. In general, an entire arrangement of the nerve endings was almost completely cut in less than ten 800-nm thick sections instead of the 50- to 100-ultrathin (ie, less than 100 nm) conventional sections for transmission electron microscopy. The present study confirms an earlier report that the first row outer hair cells in the third cochlear turn are innervated by nearly equal numbers of efferent and afferent endings, the average number being nine.

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